1. Field of the Invention
The present invention relates to an apparatus for measuring a sighting direction of eyes, for example a driver's eyes, in a noncontact manner.
2. Description of the Prior Art
An example of a conventional apparatus for measuring a sighting direction of eyes is disclosed in Japanese Laid-Open Patent Publication No. 2-134130. This conventional apparatus employs two cameras spaced apart from each other. One of the cameras is coaxial with a light source. Each camera picks up an image of the corneal sphere of an eye of an objective person. On each of the picked up images, the coordinates of the reflection of the light source are connected to the coordinates of the camera, to find an expression representing a straight line passing through the center of the corneal sphere. At the same time, the coordinates of the center of the pupil of the eye are found. An intersection of the straight lines obtained with the two cameras determines the coordinates of the center of the corneal sphere, and a straight line connecting the center of the corneal sphere to the center of the pupil determines the sighting direction of the eye. This apparatus employs two cameras, and therefore, is expensive. This is a problem.